!+
! Subroutine track1_custom (orbit, ele, param, err_flag, finished, track)
!
! Dummy routine for custom tracking. 
! This routine needs to be replaced for a custom calculation.
! If not replaced and this routine is called, this routine will generate an error message.
!
! Also see:
!   track1_preprocess
!   track1_postprocess
!
! If this routine takes into account radiation damping and/or excitation when bmad_com%radiation_damping_on 
! and/or bmad_com%radiation_fluctuations_on is True, a custom version of track1_preprocess should be 
! constructed to set its radiation_included argument to True.
! If not, the track1 routine will use track1_radiation to include the radiation effects.
! Note: If this routine calles symp_lie_bmad, the symp_lie_bmad routine does take into account radiation effects.
!
! Note: If ele%spin_tracking_method = tracking$, then it is expected that this routine will also handle
! spin tracking. The alternative is when ele%spin_tracking_method = custom$ in which case track1_spin_custom will
! be called after this routine. If doing spin tracking here, bmad_com%spin_tracking_on should be checked
! to see if spin tracking is actually wanted.
!
! General rule: Your code may NOT modify any argument that is not listed as an output agument below.
!
! Input:
!   orbit      -- coord_struct: Starting position.
!   ele        -- ele_struct: Lattice element.
!   param      -- lat_param_struct: Lattice parameters.
!
! Output:
!   orbit       -- coord_struct: End position.
!   err_flag    -- logical: Set true if there is an error. False otherwise.
!   finished    -- logical: When set True, track1 will halt processing and return to its calling routine.
!   track       -- track_struct, optional: Structure holding the track information if the 
!                    tracking method does tracking step-by-step.
!-

subroutine track1_custom (orbit, ele, param, err_flag, finished, track)

use bmad, except_dummy => track1_custom

implicit none

type (coord_struct) :: orbit
type (ele_struct) :: ele
type (ele_struct), pointer :: lord
type (lat_param_struct) :: param
type (track_struct), optional :: track

logical err_flag, finished

character(*), parameter :: r_name = 'track1_custom'

! 

call out_io (s_fatal$, r_name, 'THIS DUMMY ROUTINE SHOULD NOT HAVE BEEN CALLED BY ELEMENT: ' // ele%name, &
                               'EITHER CHANGE THE TRACKING_METHOD OR LINK THIS PROGRAM TO AN APPROPRIATELY MODIFED TRACK1_CUSTOM ROUTINE.')
err_flag = .true.

! Remember to also set orbit%t

orbit%s = ele%s 

! If ele represents a section of the entire element and the element has internal structure (not uniform
! longitudinally), then it will be important to know the position of ele relative to the entire element.
! The entire element will be the lord:

if (ele%slave_status == slice_slave$ .or. ele%slave_status == super_slave$) then
  lord => pointer_to_lord(ele, 1)
  ! Now [lord%s_start, lord%s] is the position of the entire element.
endif


end subroutine